An epitaxial growth method can grow on a crystal substrate a single crystal having a crystal orientation identical to that of the crystal substrate, and thus is used in various fields.
For example, the following Patent Documents 1 and 2 describe methods for manufacturing a silicon wafer by an epitaxial growth method of Si.
In the above epitaxial growth method, it is preferable that a substrate, on which a predetermined film grows, is heated to a temperature higher than the decomposition temperature of a source gas so that the source gas can be thermally decomposed. Accordingly, induction heating using a coil may be used to heat the substrate for example.    Patent Document 1: Japanese Patent Laid-open Application No. H9-232275    Patent Document 2: Japanese Patent Laid-open Application No. 2004-323900
However, a source gas may have a high thermal decomposition temperature. In such a case, it is required to increase the temperature of the substrate to be higher than the thermal decomposition temperature, which makes it difficult to use the induction heating for a film forming apparatus. For example, in the induction heating using a coil, a power conversion efficiency, i.e., the ratio of thermal energy for heating the substrate to input electric power, is low, resulting in the reduced power utilization efficiency.
Accordingly, especially when decomposing a film forming gas having a high thermal decomposition temperature, the amount of input electric power for induction heating increases, and the cost for film formation increases. Further, in order to heat a substrate to a high temperature, a high frequency electric power supply for induction heating needs to be scaled up and, also, a high frequency shielding structure has to be scaled up and complex, resulting in a scaled up and complicated film forming apparatus.
One of the reasons for the deterioration of the conversion efficiency of the induction heating is that it is difficult to install a coil used for the induction heating near a substrate. For example, the coil for the induction heating is installed outside a processing chamber made of a material having a low dielectric loss, e.g., quartz or the like, and thus cannot be installed near the substrate provided inside the corresponding processing chamber.
On the other hand, in case of a direct heating of a substrate by a heater, the substrate may not be heated to a decomposition temperature of a film forming gas, depending on the film forming gas. For instance, a hydrocarbon-based gas (e.g., a gas represented by CxHy (x and y being integers)) generally has a high thermal decomposition temperature. As an example, a decomposition temperature of C3H8 is about 1200° C., so that the substrate needs to be heated to a temperature higher than or equal to 1200° C. Further, in order to obtain a sufficient film deposition rate and a high film quality, the substrate needs to be heated to about 1500° C. Accordingly, the heater also needs to be heated to a temperature higher than or equal to about 1500° C. However, within the knowledge of the inventors of the present invention, there has never been employed a heater which can endure such high temperature.
Moreover, the heater is provided inside the processing chamber which is maintained in a vacuum state, thereby causing the degassing or the thermal decomposition (sublimation) of the heater itself.